Monitoring apparatus for monitoring the operation of single-seed drills are known in different versions. Often the monitoring is carried out on a conveying channel due to easy accessibility, as for example in document WO 2005/096799 A1 or WO 2005/096798 A1.
Monitoring apparatus are used among others for control and adjustment as well as checking of the proper operation of the sowing sets. There is a requirement that the monitoring responds quickly and works easily and without problems. Furthermore the monitoring apparatus should work as economically and maintenance-free as possible.